#include<iostream>
#include<vector>
#include<algorithm>
#include<string>
using namespace std;

class Solution {
public:
    int trailingZeroes(int n) {
        int count = 0;
        while(n>0){
            count += n/5;
            n = n/5;
        }
        return count;
    }
};

int main(){
    Solution S;
    cout<<S.trailingZeroes(25)<<endl;
}